cv::destroyAllWindows() yields an error if no window exists. (Bug #2440)

I use the latest Git version of OpenCV (I am not sure how to obtain the Git version hash) on Windows 7, x64, built with QT 4.8.4 and MSVC 9.0 SP1.

Code to reproduce error:

#include <cstdio>
#include <cstdlib>
#include <string>
#include <iostream>
#include <algorithm>
#include <vector>

#include <cxcore.h>
#include <cv.h>
#include <highgui.h>

int main(int argc, char* argv[])
{
    // crashes on Windows 7 x64, OpenCV built with Qt 4.8.4
    cv::destroyAllWindows(); 

    return 0;
}

Error message:

OpenCV Error: Null pointer (NULL guiReceiver (please create a window)) in unknow
n function, file ..\..\..\opencv-git\modules\highgui\src\window_QT.cpp, line 502

Possible fix:
Replace

CV_IMPL void cvDestroyAllWindows()
{
    if (!guiMainThread)
        CV_Error( CV_StsNullPtr, "NULL guiReceiver (please create a window)" );

    QMetaObject::invokeMethod(guiMainThread,
        "destroyAllWindow",
        //Qt::BlockingQueuedConnection,
        Qt::AutoConnection);
}

CV_IMPL void cvDestroyAllWindows()
{
    if (!guiMainThread)
        return;

    QMetaObject::invokeMethod(guiMainThread,
        "destroyAllWindow",
        //Qt::BlockingQueuedConnection,
        Qt::AutoConnection);
}